/Engine/Source/Editor/UnrealEd/Classes/Editor/EditorEngine.h
Takes a list of polygons and returns a list of the outside edges (edges which are not shared by other polys in the list).
virtual void polyGetOuterEdgeList ( [TArray](API\Runtime\Core\Containers\TArray)< [FPoly](API\Runtime\Engine\Engine\FPoly) > * InPolyList, [TArray](API\Runtime\Core\Containers\TArray)< [FEdge](API\Runtime\Core\Math\FEdge) > * InEdgeList )